Hydraulic cylinders are commonly used to deliver reciprocating linear forces in a wide variety of mechanical applications. The essential components of a hydraulic cylinder include a cylinder barrel, a piston that moves linearly within the cylinder barrel, a pressurized hydraulic fluid sealed within the cylinder barrel that activates the movement of the piston, a piston rod attached to the piston that delivers a reciprocating, linear force as the piston is moved within the cylinder barrel, a blind end cap or other closure that seals and contains the hydraulic fluid on the blind end of the cylinder barrel and a rod end assembly that seals and contains the hydraulic fluid on the rod end of the cylinder barrel but also allows the piston rod to reciprocate freely through the rod end of the cylinder barrel.
A rod gland is typically utilized in the rod end of the cylinder to seal the end of the barrel. The rod gland must be prevented from either slipping out of or farther into the cylinder barrel. Many configurations for holding the rod gland in place have been utilized. The rod gland may be held in place by a gland nut or collar that is screwed, welded or otherwise secured to the rod end of the barrel. Although widely employed, these configurations have inherent weaknesses.
In configurations where the gland nut is screwed to the barrel, the outside of the cylinder barrel must be machined to create threads, which is an expensive operation that may also weaken the barrel. In addition, hydraulic cylinders are subject to vibration and other forces that can, over a period of time, cause threaded components to unscrew. Threaded metal components can also be difficult to engage and disengage. The threads can be stripped, which can ruin the components or lead to expensive remachining operations. Threaded metal components may also rust or corrode, making it difficult to remove the gland nut.
In configurations where the gland nut is welded to the barrel, the cylinder barrel may be damaged or distorted by the heat of the welding operation. Seals within the cylinder barrel can also be damaged by the heat of welding on the exterior of the barrel. Further, once the gland nut is welded to the barrel, it cannot be easily removed and seals and components within the barrel cannot be easily accessed for repair or replacement.
Also, whether screwed or welded to the rod end of the cylinder barrel, the gland nut adds significant bulk to the rod end of the hydraulic cylinder, and creates a snag point and protrusion on an otherwise streamlined cylinder. In certain applications, this additional bulk on the end of the cylinder can be a significant disadvantage.
In addition to preventing the rod gland from sliding out of the cylinder barrel, the rod gland must also be prevented from sliding farther into the cylinder barrel. Tapered or enlarged cylinder barrels have been developed that prevent the rod gland from sliding into the cylinder, but these configurations have been overly complex or otherwise inadequate. U.S. Pat. No. 5,715,740 issued to Sims utilizes a tapered cylinder barrel coupled with a threaded retaining ring that engages threads on the interior of the barrel. This configuration, however, is complex to machine, difficult to disassemble and requires the use of specialized tools to assemble and disassemble. U.S. Pat. No. 3,881,401 issued to Bimba also employs a threaded end member that engages threads on the interior of the cylinder barrel. The threaded end member is held in place by a spring wire member that secures the threaded end member in place.
These configurations, however, require that the interior of the barrel be machined to create threads, which is an expensive machining process and can compromise the integrity of the barrel. The threaded components also can become stripped or cross-threaded, leading to problems with the assembly and disassembly of the hydraulic cylinder. Further, the interior threads create sharp snag points on the interior of the barrel that can damage seals on the rod gland when the rod gland is inserted into or removed from the barrel.
Another use of a tapered or enlarged barrel is disclosed in U.S. Pat. No. 4,085,661 issued to Schriever. In this configuration, despite the use of an enlarged barrel, the rod gland is secured to both a gland nut and the cylinder barrel. In particular, a plurality of wedge-shaped locking segments are bolted to the cylinder barrel and an annular cap is bolted to the rod gland with locking bolts. Locking bolts, however, may become loose due to vibration or other forces, suffer from cross-threading and stripping problems, create additional complexity for the rod end assembly and protrude from the cylinder to create additional snag points. This solution is therefore not optimal.
Accordingly, an object of the present invention is to provide an improved hydraulic cylinder with a streamlined cylinder barrel free of protrusions and snag points.
A further object of the present invention is to provide an improved hydraulic cylinder that eliminates the need for a gland nut or collar to hold the rod gland in place.
Another object of the present invention is to provide an improved hydraulic cylinder without threaded components, thereby preventing the possibility that the components could become unscrewed during use of the hydraulic cylinder and eliminating other problems associated with threaded components.
An additional object of the present invention is to provide an improved hydraulic cylinder that may be assembled without welding any of the components.
A still further object of the present invention is to provide an improved hydraulic cylinder that may be easily assembled and disassembled without special tools.
Yet another object of the present invention to provide an improved hydraulic cylinder without snag points on the interior of the rod end of the barrel to prevent damage to seals when the rod gland is inserted into or removed from the barrel.
Finally, an object of the present invention is to provide an improved hydraulic cylinder that is economical to manufacture and refined in appearance.